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b=UmAJp2HGw6a1cxu8Z7qUN33jlTIG2j+zWU8WRaBYMPD0e82ko/eZ36AgAOa43kY/h lxlrudp9simk7JoBMca54NyZEiKzJWI3xHq2I1kMIbJ1GduGALBQqbCBcYKGWYTFml 5vfTpJMEs/Ewmp3fN/cMWDpJaVYBCErmVSoa/nVd3BNHzL1DSVVHXG8CYdXTe5g+EE xDYke9gzTLyp1NWBse1zzjPaNGj6xpmesgfWQ6pdUmfK2zOnhfdz4GuStr5vUNRqfT EAl2lV0KWC1COJwOyO0SXjG50HaGTpdkfNeGrd4M9vMiPC4pKJCOBSsVBpQaOqYjgK 0CNto2tHZMgOA== From: Pratyush Yadav To: Mike Rapoport Cc: Tarun Sahu , Pasha Tatashin , Pratyush Yadav , Andrew Morton , linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org Subject: Re: [PATCH] mm/memfd_luo: validate serialized_data before conversion In-Reply-To: (Mike Rapoport's message of "Thu, 11 Jun 2026 15:40:03 +0300") References: Date: Thu, 11 Jun 2026 15:37:12 +0200 Message-ID: <2vxzmrx1qjuf.fsf@kernel.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Queue-Id: 7E902A000E X-Rspam-User: X-Stat-Signature: jkyqey3tao6bzh998p5grmp6rsripk9s X-Rspamd-Server: rspam09 X-HE-Tag: 1781185036-860502 X-HE-Meta: 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 KKitRcUc QddvP/owQihAwDi8qbANiTW00G6jx5YskhsG7J5q5qOXYvKH6XHMKUU9iJxHjBH+UTeM0QLZRaoHqdFmgxpl9EtBFhqK1jBNi2C4Hpq2CFrg4QyYNytsyY0nG683VJbuwn3WOWzP1Oy3cfSP9z3W1bpxYjSgvdxGBqZKjIA4b1N2GnqEfg3iAsk/65HX1M59jTc0XdpmZpoWCGlde0l6+eBTaC6qDlojyU1t9d9P3T68OBVnidHSQOav6Iv7nC2qtRdIVuMrQyDcxEzsaWDEUjNG/UQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Jun 11 2026, Mike Rapoport wrote: > On Thu, Jun 11, 2026 at 10:30:03AM +0000, Tarun Sahu wrote: >> In memfd_luo_finish() and memfd_luo_retrieve(), phys_to_virt() was called >> on args->serialized_data before checking if the physical address is valid. >> Since physical address 0 does not map to virtual NULL (due to direct >> mapping offsets), the subsequent check 'if (!ser)' was ineffective at >> catching a missing serialized_data, leading to unsafe dereferences later. >> >> Validate that args->serialized_data is non-zero before calling >> phys_to_virt(). >> >> Fixes: b3749f174d68 ("mm: memfd_luo: allow preserving memfd") >> Signed-off-by: Tarun Sahu >> --- >> mm/memfd_luo.c | 10 ++++++---- >> 1 file changed, 6 insertions(+), 4 deletions(-) >> >> diff --git a/mm/memfd_luo.c b/mm/memfd_luo.c >> index 59de210bee5f..10f3983b0060 100644 >> --- a/mm/memfd_luo.c >> +++ b/mm/memfd_luo.c >> @@ -397,10 +397,11 @@ static void memfd_luo_finish(struct liveupdate_file_op_args *args) >> if (args->retrieve_status) >> return; >> >> - ser = phys_to_virt(args->serialized_data); >> - if (!ser) >> + if (!args->serialized_data) > > We really should make args->serialized_data a KHOSER_PTR Hmm, that would also be a good idea. I suppose then it would be a better to directly convert to using KHOSER_PTR() instead of this patch? > >> return; >> >> + ser = phys_to_virt(args->serialized_data); >> + >> if (ser->nr_folios) { >> folios_ser = kho_restore_vmalloc(&ser->folios); >> if (!folios_ser) >> @@ -522,10 +523,11 @@ static int memfd_luo_retrieve(struct liveupdate_file_op_args *args) >> struct file *file; >> int err; >> >> - ser = phys_to_virt(args->serialized_data); >> - if (!ser) >> + if (!args->serialized_data) >> return -EINVAL; >> >> + ser = phys_to_virt(args->serialized_data); >> + >> /* Make sure the file only has seals supported by this version. */ >> if (ser->seals & ~MEMFD_LUO_ALL_SEALS) { >> err = -EOPNOTSUPP; >> >> base-commit: 9716c086c8e8b141d35aa61f2e96a2e83de212a7 >> -- >> 2.54.0.1099.g489fc7bff1-goog >> -- Regards, Pratyush Yadav